Search results for query: *

Sorry, IR values are in G Ohm.

Hi, we have done straight through jont in a 33 kV UE 1c cable. After jointing, when we took the PI, PI is coming very high (more than 50 with 1 min & 10 min value as 5.98 and 342 M Ohm respectively). Can any one explain the phenomena pls?

Dear All, We are having a 16 MW 11 kV Generator. Recently thrust pad of machine got damaged. Mechanical team is fearing that it may be due to improper magnetic center of Generator. Please guide me on following: 1. If thrust pad can get damage due to improper magnetic center? 2. How to test that...

Oil for all the voltage level is same. Only difference is in its BDV and PPM level. For higher voltage level e.g. 200 kV system, desirable BDV is 70 kV and PPM is 100, whereas for lower voltage level e.g. 33 kV, 55 kV and 20 PPM might be acceptable.

Hi, Kindly help me in getting / knowing the acceptable value of leakage current (fundamental as well as 3rd harmonic) for LA in 220 kV system? Regards,

Hi PRC, Can you please share, how did you calculate the various impedance?

Thanks Marmite, But in hilly area, where improving the earth resistance is challenge, how the energy of LA will dissipate, if we install LA across the insulator string?

It has static wire in the form of OPGW.

I am having about 60 KM long 220 kV double circuit Transmission line, which passes through the forest and hilly area. During rainy season, heavy lightening takes place and causes the frequent tripping of line and on checking, we often find flash marks on the disc. Quite often, we found the flash...

Hi During routine inspection, we observed that counter reading of one of the 220 kV LA's has increased to 76 from 21 in one week time. I am arraning for checking the 3rd harmonic leakage current. Is there any specific reason for this sudden increase in counter reading can be ascertained and...

Thanks Cuky, is there a way by which i can check the presence of ferroresonance? There is no visible sign (hunting etc.) of ferroresonance in our system.

Yes, our system is effectively grounded. I don't have any idea, how rated voltage was selected. Is there any guidelines for its selection in case of LAs?

@ PWRTRAN: How can we check / test the LAs for manufacturing / design problem. Can you suggest some change in specification / inclusion of tests while ordering? we are monitoring the 3rd harmonic leakage current periodically and it is in the order. @ Rasevskii: LAs are vertically mounted with...

We have are supplying power to our Oxygen plant through 1.5 KM long cables. Cables are terminated to a 25 MVA Ynyn Transformer (33 kV / 6.6 kV) in open yard. LAs are provided just before the Transformers. Name plate details of LAs are: Metal Oxide, Rated voltage - 36 kV, Discharge current - 20...

Our AVRs are always in the Auto mode and we keep excitation in lagging mode. I am very much sure about the agreement with Unitlity and i can island myself based on our requirement.

Thanks a lot Mr Raghun. I also agree that we should not unnecessarily island our self during disturbance in the Grid. But we are not primarily generating company. We are industry having our captive Generators and we want to save our critical load along with captive generators from tripping by...

We are having a large industrial load with about 500 MW internal generation. Our plant normally operates in parallel with Grid. In recent past, there had been severe frequency fluctuation in the Grid, which resulted into tripping of some of our internal Generators because of delayed islanding...

Thanks Mr Slava, well in interested to know the application of HI & LI differential protection be it 87G, 87T, 87N, 87B. I mean for which protection HI or LI should be used and why?

I want to know, where should we use high impedance differential protection and where low impedance should be used. What are the advantages & disadvantages of both schemes?

Metrosil is a device which protects equipment from over voltages. In protection circuit, it is normally used across the differential relays.